Exploring cellular uptake of iron oxide nanoparticles associated with rhodium citrate in breast cancer cells.

Nanocarriers have the potential to improve the therapeutic index of currently available drugs by improving their efficacy and achieving therapeutic steady-state levels over an extended period. The association of maghemite-rhodium citrate (MRC) nanoparticles (NPs) has the potential to increase specificity of the cytotoxic action. However, the interaction of these NPs with cells, their uptake mechanism, and subcellular localization need to be elucidated. This work evaluates the uptake mechanism of MRC NPs in metastatic and nonmetastatic breast cancer-cell models, comparing them to a nontumor cell line. MRC NPs uptake in breast cancer cells was more effective than in normal cells, with regard to both the amount of internalized material and the achievement of more strategic intracellular distribution. Moreover, this process occurred through a clathrin-dependent endocytosis pathway with different basal expression levels of this protein in the cell lines tested.

In vitro permeation of platinum and rhodium through Caucasian skin.

During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace.

Biological effects of simple changes in functionality on rhodium metalloinsertors.

DNA mismatch repair (MMR) is crucial to ensuring the fidelity of the genome. The inability to correct single base mismatches leads to elevated mutation rates and carcinogenesis. Using metalloinsertors-bulky metal complexes that bind with high specificity to mismatched sites in the DNA duplex-our laboratory has adopted a new chemotherapeutic strategy through the selective targeting of MMR-deficient cells, that is, those that have a propensity for cancerous transformation. Rhodium metalloinsertors display inhibitory effects selectively in cells that are deficient in the MMR machinery, consistent with this strategy. However, a highly sensitive structure-function relationship is emerging with the development of new complexes that highlights the importance of subcellular localization. We have found that small structural modifications, for example a hydroxyl versus a methyl functional group, can yield profound differences in biological function. Despite similar binding affinities and selectivities for DNA mismatches, only one metalloinsertor shows selective inhibition of cellular proliferation in MMR-deficient versus -proficient cells. Studies of whole-cell, nuclear and mitochondrial uptake reveal that this selectivity depends upon targeting DNA mismatches in the cell nucleus.

First determination of the levels of platinum group metals in Manta birostris (manta ray) caught along the Ghanaian coastline.

Tissues from Manta birostris caught by fishermen from Dixcove in the western part of Ghana were analyzed for their Platinum, palladium and rhodium concentrations (PGM). The use of chondrichthyan fish has permitted the study of trace levels of Platinum group metals (PGMs) which have travelled very far into the sea. The analysis showed that Ghana's coastline is fairly polluted with these platinum group metals (PGMs). PGM concentration in manta ray recorded a range of (0.15-0.85) microg/g for Pt, (0.033-0.67) microg/g for Pd and (0.007-0.145) microg/g for Rh. Comparing these values to the UK dietary intake of 0.2 microg/day for Pt and Rh and 1.0 microg/day for Pd, its indicates that the values obtained from the analysis for Pt was above the required level. This is the first study to show the accumulation of PGM in chondrichthyan fish, although the sources of this pollution are not clear as manta birostris is migratory and therefore need to be investigated further. The presence of the PGM is very significant, since manta ray meat is consumed in Ghana. This may presents a health risk, due to a possible accumulation of PGMs in humans.

Airborne particulate matter, platinum group elements and human health: a review of recent evidence.

Environmental concentrations of the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) have been on the rise, due largely to the use of automobile catalytic converters which employ these metals as exhaust catalysts. It has generally been assumed that the health risks associated with environmental exposures to PGE are minimal. More recent studies on PGE toxicity, environmental bioavailability and concentrations in biologically relevant media indicate however that environmental exposures to these metals may indeed pose a health risk, especially at a chronic, subclinical level. The purpose of this paper is to review the most recent evidence and provide an up-to-date assessment of the risks related to environmental exposures of PGE, particularly in airborne particulate matter (PM). This review concludes that these metals may pose a greater health risk than once thought for several reasons. First, emitted PGE may be easily mobilised and solubilised by various compounds commonly present in the environment, thereby enhancing their bioavailability. Second, PGE may be transformed into more toxic species upon uptake by organisms. The presence of chloride in lung fluids, for instance, may lead to the formation of halogenated PGE complexes that have a greater potential to induce cellular damage. Third, a significant proportion of PGE found in airborne PM is present in the fine fraction that been found to be associated with increases in morbidity and mortality. PGE are also a concern to the extent that they contribute to the suite of metals found in fine PM suspected of eliciting a variety of health effects, especially in vulnerable populations. All these factors highlight the need to monitor environmental levels of PGE and continue research on their bioavailability, behaviour, speciation and associated toxicity to enable us to better assess their potential to elicit health effects in humans.

The estimation of the bioavailabilities of platinum, palladium and rhodium in vehicle exhaust catalysts and road dusts using a physiologically based extraction test.

Platinum group element (PGE) levels in the environment have increased following the introduction of vehicle exhaust catalysts (VECs). In order to evaluate the potential pathways of PGEs from VECs into humans, a physiologically based extraction test (PBET) was used to study the uptake of PGEs by the human digestive tract. The PBET assay was implemented in two phases, to first simulate the passage of ingested soil through the acid conditions of the stomach before it enters the near neutral conditions of the small intestine. The results showed that Pt, Pd and Rh did not undergo precipitation reaction when passing from the acid environment of the stomach to the neutral environment of the small intestine. The greatest fractions of bioavailable PGEs (up to 68%) were observed in road dust samples, possibly due to the presence of mobile PGE species formed in the roadside environment. Higher percentages of Pd and Rh were bioavailable than Pt, probably due to the differences in their mobilities and tendencies to form soluble complexes. Pt showed the highest absolute bioavailability however, due to its greater concentration in environmental samples. The solubilization of PGEs in the human digestive tract could involve the formation of PGE-chloride complexes, with perhaps increased health-hazard issues because of the known toxic and allergenic effects of these species.

Impact of humic substances on the aqueous solubility, uptake and bioaccumulation of platinum, palladium and rhodium in exposure studies with Dreissena polymorpha.

Zebra mussels (Dreissena polymorpha) were exposed to different types of water containing PGE salts (PtCl4, PdSO4, RhCl3) to investigate the influence of humic substances on the aqueous solubility, uptake and bioaccumulation of noble metals. The results showed a time dependent decrease of the aqueous PGE concentrations in tank water for all groups. This could mainly be related to non-biological processes. The aqueous solubility of Pd and Rh was higher in humic water compared with non-chlorinated tap water, whereas Pt showed opposing results. Highest metal uptake rates and highest bioaccumulation plateaus were found for Pd, followed by Pt and Rh. Pd uptake and bioaccumulation was significantly hampered by humic substances, whose presence appear to increase Pt uptake and bioaccumulation. No clear trend emerged for Rh. Differences in effects of humic matter among the PGE may be explained by formation of metal complexes with different fractions of humic substances.

Recovery of rhodium(III) from solutions and industrial wastewaters by a sulfate-reducing bacteria consortium.

A quantitative analysis of the rate of removal of rhodium(III) by a resting sulfate-reducing bacteria (SRB) consortium under different initial rhodium and biomass concentrations, pH, temperature, and electron donor was studied. Rhodium speciation was found to be the main factor controlling the rate of its removal from solution. SRB cells were found to have a higher affinity for anionic rhodium species, as compared to both cationic and neutral species, which become abundant when speciation equilibrium was reached. Consequently, a pH-dependent rate of rhodium removal from solution was observed. The maximum SRB uptake capacity for rhodium was found to be 66 mg of rhodium per gram of resting SRB biomass. Electron microscopy studies revealed a time-dependent localization and distribution of rhodium precipitates, initially intracellularly and then extracellularly, suggesting the involvement of an enzymatic reductive precipitation process. When a purified hydrogenase enzyme was incubated with rhodium chloride solution under hydrogen, 88% of the rhodium was removed within 1 h, whereas with a soluble extract from SRB 77% was removed within 10 min. Due to the low pH of the industrial effluent (1.31), the enzymatic reduction of rhodium by the purified hydrogenase was greatly limited, and it was apparent that an industrial effluent pretreatment was necessary before the application of an enzymatic treatment. In the present study, however, it was established that SRB are good candidates for the enzymatic recovery of rhodium from both aqueous solution and industrial effluent.

Uptake and bioaccumulation of platinum group metals (Pd, Pt, Rh) from automobile catalytic converter materials by the zebra mussel (Dreissena polymorpha).

The uptake and bioaccumulation of the platinum group metals (PGM) platinum (Pt), palladium (Pd), and rhodium (Rh) by the zebra mussel (Dreissena polymorpha) were investigated in exposure studies using ground material from unused automobile catalytic converters as metal source. The mussels were exposed to the metals in tap water or humic water. In the soft tissue samples of exposed mussels mean Pt levels ranged in dependence on the type of tank water and the exposure period (6, 9, or 18 weeks) between 780 and 4300 ng/g, the Pd levels ranged between 720 and 6300 ng/g, and the Rh levels ranged between 270 and 1900 ng/g. In contrast, the control mussels had metal concentrations of <20 ng/g (Pt), <50 ng/g (Pd), and <40 ng/g (Rh). Considerably higher PGM levels were found in the exposed mussels of the humic water group than in those of the tap water group. Although there is a cumulative increase of the PGM concentrations in the environment since the introduction of the automobile catalyst more than 20 years ago, only little information about the PGM contamination in the biosphere, especially the fauna, is available. Due to the high capacity of D. polymorpha to accumulate PGM, this bivalve could be used as a potential sentinel for monitoring the noble metals in aquatic ecosystems.

Environmental routes for platinum group elements to biological materials--a review.

The increased use of platinum group elements (PGE) in automobile catalysts has led to concern over potential environmental and biological accumulation. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations have increased in the environment since the introduction of automobile catalysts. This review summarises current knowledge concerning the environmental mobility, speciation and bioavailability of Pt, Pd and Rh. The greater proportion of PGE emissions is from automobile catalysts, in the form of nanometer-sized catalyst particles, which deposit on roadside surfaces, as evidenced in samples of road dust, grass and soil. In soil, PGE can be transformed into more mobile species through complexation with organic matter and can be solubilised in low pH rainwater. There are indications that environmentally formed Pd species are more soluble and hence more mobile in the environment than Rh and Pt. PGE can reach waterbodies through stormwater transport and deposition in sediments. Besides external contamination of grass close to roads, internal PGE uptake has been observed for plants growing on soil contaminated with automobile catalyst PGE. Fine particles of PGE were also detected on the surface of feathers sampled from passerines and raptors in their natural habitat, and internal organs of these birds also contained PGE. Uptake has been observed in sediment-dwelling invertebrates, and laboratory studies have shown an uptake of PGE in eel and fish exposed to water containing road dust. The available evidence indicates that the PGE, especially Pd, are transported to biological materials through deposition in roots by binding to sulphur-rich low molecular weight species in plants. PGE uptake to exposed animals have uptake rates in the following order: Pd>Pt>Rh. The liver and kidney accumulate the highest levels of PGE, especially Pd. Urinary Pd and Rh, but not Pt, levels are correlated with traffic intensity. Dental alloys may lead to elevated urinary Pt levels. Platinum is a well-known allergen and Pd also shows a strong sensitisation potential.

Platinum group elements in raptor eggs, faeces, blood, liver and kidney.

The increased use of platinum group elements (PGEs) in automobile catalysts and their emission into the environment has led to a concern over environmental and particularly biological accumulation. Specimens of samples from raptors are useful for the investigation of the impact of PGEs because these birds are found in both urban and rural environments and are invariably at the top of the food chain. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations were determined by quadrupole Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in eggs of the sparrowhawk (Accipiter nisus) and the peregrine falcon (Falco peregrinus), and in blood, liver and kidney of the peregrine falcon, while only Pt was determined in faeces of the peregrine falcon and the gyrfalcon (Falco rusticolus). PGE concentrations were higher in blood compared to both faeces and eggs, while liver and kidney concentrations were not elevated indicating no bioaccumulation through metallothionein pathways. A significant spatial trend could only be established for Pt in faeces. The general lack of a spatial trend is probably due to the widespread distribution of automobiles and the long-range transport of nanoparticles containing PGEs, and because birds migrate and forage over large areas. No significant temporal trend could be established. Higher relative concentrations of Pd, followed by Rh and Pt, indicate a mobility gradient of Pd>>Rh>Pt.

Significance of platinum group metals emitted from automobile exhaust gas converters for the biosphere.

INTENTION, GOAL, SCOPE, BACKGROUND: Following the introduction of automobile catalytic converters the platinum group metals (PGM) platinum (Pt), palladium (Pd) and rhodium (Rh) gain on increasing interest in environmental research as these metals are emitted with exhaust fumes into the environment. Consequently, elevated PGM levels were found in different environmental matrices such as road dusts, soils along heavily frequented roads, sediments of urban rivers etc. Accordingly, the effects of increasing PGM emissions on the biosphere are controversially discussed. OBJECTIVE: This paper summarizes the present knowledge on the biological availability of PGM to plants and animals. As biological availability is one of the most decisive factors determining the toxicological potential of xenobiotics, this information is very important to evaluate the possible threat of the noble metals to ecosystems. RESULTS AND DISCUSSION: The availability of soluble as well as particle bound PGM to terrestrial plants was demonstrated in several studies. Experimental investigations revealed uptake of Pt, Pd and Rh also by aquatic plants. Additionally, the biological availability of the noble metals for animals has been verified in experimental studies using soluble metal salts, catalytic converter model substances, sediments of urban rivers, road dust or tunnel dust as metal sources. These studies refer mainly to aquatic animals. Beside of free living organisms, in particular worms parasitizing fish demonstrated a high potential to accumulate PGM. This could be of great interest in respect of biomonitoring purposes. Generally, for plants as well as for animals Pd turns out to be the best available metal among the PGM. Compared to other heavy metals, the biological availability of PGM from road dust to zebra mussels (Dreissena polymorpha) ranged between that of Cd and Pb. CONCLUSION: Especially chronic effects of PGM on the biosphere can not be excluded due to (1) their cumulative increase in the environment, (2) their unexpected high biological availability and bioaccumulation and (3) their unknown toxicological and ecotoxicological potential. However, it appears that acute effects on ecosystems due to anthropogenic PGM emission are not likely. RECOMMENDATION AND OUTLOOK: Research on environmental PGM contamination of the biosphere, especially the fauna, and on long-term toxicity of low PGM concentrations is highly appreciated. These studies require very sensitive analytical techniques to determine PGM even in low sample amounts. Research has to be done in particular on reliable determination of (ultra) trace levels of Pd and Rh as the lack of data on these two metals is mainly due to analytical problems.

Bioaccumulation of platinum group elements and characterization of their species in Lolium multiflorum by size-exclusion chromatography coupled with ICP-MS.

The bioaccumulation of Pt, Pd and Rh by grass grown hydroponically with nutrient solutions containing these ions at elevated (38.7 mg l(-1) Pt, 21.7 mg l(-1) Pd and 7.1 mg l(-1) Rh) and medium (3.6 mg l(-1) Pt, 4.4 mg l(-1) Pd and 0.5 mg l(-1) Rh) concentrations was studied by using inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The highest bioaccumulation factors were obtained for Pd and Rh in roots and for Pt in leaves. The obtained results showed that most of the studied metals were accumulated in roots, and only a small fraction was really metabolised and transported to leaves. The multi-element capability of ICP-SFMS has been exploited to study the metabolism of platinum group elements (PGEs) in cultivated plants. The species of studied metals were extracted from roots and leaves and separated into two mass fractions by ultra-filtration. The low molecular mass (<10 kDa) fractions of the root and the leaf extracts were investigated by size-exclusion chromatography (SEC) coupled on-line to ICP-SFMS. The presence of Ca, Cu, S and C in the same fractions as Pt, Pd and Rh may indicate the interaction of PGEs with phytochelatins and carbohydrates.

Accumulation and distribution of platinum and rhodium in the European eel Anguilla anguilla following aqueous exposure to metal salts.

The platinum group metals (PGM) Pt and Rh are emitted into the environment mainly by catalytic exhaust gas converters of cars and by effluents of hospitals, which use Pt based anti-cancer drugs. However, there is still a lack of information on the availability of these precious metals to the biosphere. As PGM accumulate in sediments of aquatic ecosystems we focused our study on the uptake of the noble metals by European eels, Anguilla anguilla. Therefore, eels were exposed in tap water and humic water containing Pt(4+) and Rh(3+) at a concentration of 170 and 260 microg/l, respectively. After an exposure period of 6 weeks the mean Pt levels in bile, liver, kidney and intestine of the exposed eels ranged between 68 ng/g and 840 ng/g and the mean Rh levels between 35 ng/g and 155 ng/g whereas the PGM levels of the unexposed controls were below the detection limit of 50 ng/g for Pt and 5 ng/g for Rh. Rh was also taken up by gill and spleen. No PGM uptake was found for muscle and blood. The pattern of metal distribution within the eel differed between Pt and Rh and was dependent on the water type. Due to their accumulation capacity for PGM eels are suitable as accumulation indicators to detect PGM pollution in aquatic ecosystems.

Biological availability of traffic-related platinum-group elements (palladium, platinum, and rhodium) and other metals to the zebra mussel (Dreissena polymorpha) in water containing road dust.

The uptake and bioaccumulation of 15 road dust metals by the zebra mussel (Dreissena polymorpha) were investigated in laboratory exposure studies with emphasis on the traffic-related platinum-group elements (PGEs) palladium (Pd), platinum (Pt), and rhodium (Rh). The biological availability of the metals may depend on water characteristics, so the mussels were maintained in two types of water: nonchlorinated tap water and humic water of a bog lake, both of which contained dust of a moderately frequented road. After an exposure period of 26 weeks, soft tissues of the mussels were freeze-dried and analyzed for the metals. The metal concentrations in the mussel soft tissue ranged from several hundred micrograms per gram (e.g., for iron [Fe]) to less than 10 ng/g (for PGEs). Metal uptake from the road dust by the mussels was found for the PGEs and silver (Ag), bismuth (Bi), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), Fe, lead (Pb), and antimony (Sb). After maintenance of mussels in road dust-contaminated tap water, bioaccumulation factors (BAF = (C(exposed mussels) - C(control mussels))/C(total metal, water), where c is concentration) decreased in the following order: Cu > Cd > Ag > Pd > Sb > Pb > Fe > Pt > Rh. The biological availability of most metals was enhanced by humic water as compared to tap water. Our results show a hitherto unrecognized high availability of Pd for the mussels. Thus, this metal should be monitored more intensively in the environment to assess its distribution in the biosphere.

Relevance and analysis of traffic related platinum group metals (Pt, Pd, Rh) in the aquatic biosphere, with emphasis on palladium.

Following the introduction of automobile catalysts in the middle of the Eighties in Germany there is an increasing emission of the platinum-group-metals (PGM) platinum (Pt), palladium (Pd) and rhodium (Rh). Still, it remains unclear if these metals are bioavailable for aquatic animals and to which extent they accumulate in the aquatic biosphere. Zebra mussels (Dreissena polymorpha) were maintained in water containing road dust at a concentration of 1 kg/10 l. Following an exposure period of 26 weeks, soft tissues of the mussels were analysed applying adsorptive cathodic stripping voltammetry (ACSV) for the determination of Pt and Rh and total-reflection X-ray fluorescence analysis after co-precipitation of Pd with mercury. This experiment revealed for the first time that all the three catalyst emitted metals were accumulated by mussels. The bioaccumulation increased in the following manner: Rh < Pt < Pd. Thus, the application of sentinel organisms in combination with modern trace analytical procedures in environmental impact studies does allow an assessment of the distribution and the degree of bioaccumulation of PGM in the environment, which is highly appreciated.

Platinum group elements in the feathers of raptors and their prey.

Platinum (Pt), palladium (Pd), and rhodium (Rh) concentrations were determined in the feathers of three raptor species in Sweden, the sparrowhawk ( Accipiter nisus), the peregrine falcon ( Falco peregrinus), and the gyrfalcon ( Falco rusticolus), as well as the main prey of the sparrowhawk (the house sparrow, Passer domesticus) and the gyrfalcon (the willow grouse, Lagopus lagopus). The analysis of feathers from 1917-1999 revealed a clear temporal trend, with significantly higher Rh concentrations in sparrowhawk and peregrine falcon after 1986. There is evidence for increasing platinum group element (PGE) concentrations from 1917 to 1999 in peregrine falcon and sparrowhawk. This suggests that feathers reflect increased PGE concentrations in the environment over this time period. Mean concentrations of PGE in feathers of raptors after 1986 ranged from 0.3 to 1.8 ng x g(-1) for Pt, 0.6 to 2.1 ng x g(-1) for Pd (indicative values), and 0.1 to 0.6 ng x g(-1) for Rh. House sparrows in urban areas had significantly higher Pt and Pd concentrations than urban sparrowhawks. The higher Pd concentrations in relation to Pt and Rh may indicate the greater mobility of Pd in the environment. Although PGE concentrations are generally higher in birds living in urban areas, no significant spatial trend could be established. This is partly due to the widespread distribution of automobiles and partly because birds forage and integrate PGE exposure over large areas. Laser ablation analysis demonstrates that PGE contamination of feathers is predominantly external, consisting of small particles in the nanometer size range. Other indications of external contamination are that Pt and Pd levels are significantly higher in the vane than in the shaft and that PGE relative ratios (except Pd) reflect urban particles.

Implications of platinum-group element accumulation along U.S. roads from catalytic-converter attrition.

Automobile catalytic converters are dispersing platinum-group elements (PGEs) Rh, Pt, and Pd into the environment (1-3). This paper represents the first detailed study to assess the PGE content of soils and grasses from U.S. roadsides. These soils were analyzed using cation exchange pretreatment and ultrasonic nebulizer-ICP-MS (4). Highway and several urban sites showed Pt abundances of 64-73 ng/g immediately adjacent to the roadside, with corresponding Pd and Rh abundances of 18-31 ng/g and 3-7 ng/g, respectively. All Pt and most Pd and Rh abundances are statistically above local background soil values. Platinum, Rd, and Rh show positive correlations with traffic-related elements (Ni, Cu, Zn, and Pb) but no correlations with nontraffic-related elements (Y, Ga). Iridium and Ru show no correlations with any of these trace elements. These PGE abundances are comparable to European studies (5-7) and are approaching concentrations that would be economically viable to recover. This study also demonstrates transport of Pt statistically above background more than 50 m from the roadside. Further study is necessary to see how mobile the PGEs are in roadside environments, but these initial data indicate only Pt is taken up by plants.

First report on the uptake of automobile catalyst emitted palladium by European eels (Anguilla anguilla) following experimental exposure to road dust.

Following the introduction of automobile catalysts in the middle of the 1980s in Germany there is an increasing emission of the platinum-group-metals platinum, palladium (Pd) and rhodium. Still, it remains unclear if these metals are bioavailable for aquatic animals and to which extent they become accumulated by the aquatic biosphere. Because of analytical problems in detecting Pd in small biological samples the present investigation concentrates on the bioavailability of this metal. To answer the question of a Pd uptake by aquatic organisms experimental studies were conducted with European eels maintained in water containing road dust at a concentration of 10 kg/100 l. Following an exposure period of four weeks, samples of liver and kidney were analysed by total-reflection X-ray fluorescence analysis after co-precipitation of Pd with mercury. These experiments revealed an uptake of traffic related Pd by European eels which showed a mean liver Pd concentration of 0.18 +/- 0.05 ng/g (wet wt.), whereas the Pd concentration in the kidney ranged below the detection limit. Thus, in this study we can demonstrate for the first time that automobile catalyst emitted Pd is bioavailable for aquatic animals.

Bioaccumulation of palladium, platinum and rhodium from urban particulates and sediments by the freshwater isopod Asellus aquaticus.

The three-way catalytic converters introduced to oxidize and reduce gaseous automobile emissions represent a source of platinum group elements (PGEs), in particular platinum, palladium and rhodium, to the urban environment. Abrasion of automobile exhausts leads to an increase of the concentration of PGEs in environmental matrices such as vegetation, soil and water bodies. The bioaccumulation of Pd, Pt and Rh by the freshwater isopod Asellus aquaticus was studied in natural ecosystems and under laboratory conditions. Owing to the low concentration level (ng g(-1)) of PGEs in the animals studied. analyses were performed with a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) and hafnium, copper, yttrium, rubidium, strontium and lead were monitored for spectral interference correction. Asellus aquaticus collected in an urban river showed a content (mean +/- s) of 155.4 +/- 73.4, 38.0 +/- 34.6, and 17.9 +/- 12.2 ng g(-1) (dry weight) for Pd, Pt and Rh, respectively. The exposure of Asellus aquaticus to PGE standard solutions for a period of 24h give bioaccumulation factors of Bf: 150, 85, and 7 for Pd, Pt and Rh, respectively. Exposure of Asellus aquaticus to environmental samples for different exposure periods demonstrated that PGE bioaccumulation is time dependent. and shows a higher accumulation for the materials with a higher PGE content. While all three elements have the same uptake rate for exposure to catalyst materials, for exposure to environmental materials they havc a different uptake rate which can be attributed to transformations of the PGE species in the environment.